Cams are mechanical components widely used in various machines and automation equipment. The cam makes its follower to produce a prescribed motion through direct contact in order to achieve required motion control. Generally, the profile of a disk cam is machined by using a computer numerical control (CNC) machine, and the profile surface of the disk cam is then ground in order to achieve good surface roughness. An excessive surface roughness value of the cam profile will increase the degree of wear between the disk cam and the follower in contact with each other. Such a situation will also influence the dynamic performance of the cam mechanism so as to produce excessive vibration and noise in high-speed operations. Therefore, after the manufacturing processes for the disk cam, the surface roughness value of the disk cam must be inspected for quality control.
The surface roughness value of the disk cam could to be measured by using a conventional contact type measuring equipment. A stylus of the contact type measuring equipment contacts a part of the cam surface to measure the surface roughness value at this part. However, the measured part of the cam surface cannot have too large curvature change; otherwise, this measured part will exceed a measurable range of the stylus. In other words, a traverse length of the contact type measuring equipment should be set to a quite small value so as to ensure that the measured part of the cam surface where the stylus contacts has extremely small curvature change, which causes a low measuring efficiency of the contact type measuring equipment. Further, since the stylus of the contact type measuring equipment contacts the cam frequently during the measurement, gradual wear of the stylus will unavoidably occur.